Update postMessage support for ie11

postMessage is not supported for cross domain window communication as per:

http://stackoverflow.com/questions/21070553/postmessage-still-broken-on-ie11
http://blogs.msdn.com/b/ieinternals/archive/2009/09/16/bugs-in-ie8-support-for-html5-postmessage-sessionstorage-and-localstorage.aspx
https://connect.microsoft.com/IE/feedbackdetail/view/961901
Merge pull request #717 from neilsarkar/patch-1

Update postMessage support for ie11